In an exclusive interview with ABC News, President Obama spoke on a range of high-profile issues, including his outlook for the on-going budget negotiations, whether the Chinese government is behind the recent spate of cyberattacks against U.S. companies, North Korea's nuclear threats, same-sex marriage, and the conclave to select the next pope.

Obama Pessimistic About Grand Bargain Before Meetings With GOP Lawmakers

Before meetings with GOP lawmakers in the House and Senate today and Thursday, President Obama signaled pessimism about the prospect of reaching a grand bargain in the ongoing budget negotiations. He said there is not an "immediate debt" crisis and that, ultimately, there might just be too much space between the two parties to reach a deal.

"Ultimately, it may be that the differences are just too wide. It may be that, ideologically, if their position is, 'We can't do any revenue,' or, 'We can only do revenue if we gut Medicare or gut Social Security or gut Medicaid,' if that's the position, then we're probably not going to be able to get a deal," the president told me.

"That won't … create a crisis," he said. "It just means that we will have missed an opportunity. I think that opportunity is there and I'm going to make sure that they know that I'm prepared to work with them. But, ultimately, it may be better if some Democratic and Republican Senators work together."

Examining the Possibility of Restoring Some White House Tours

"What I'm asking them is are there ways, for example, for us to accommodate school groups … who may have traveled here with some bake sales. Can we make sure that - kids, potentially, can … still come to tour?" he said.

"But… I'm always amused when people on the one hand say, the sequester doesn't mean anything and the administration's exaggerating its effects; and then whatever the specific effects are, they yell and scream and say, 'Why are you doing that?'" he said. "Well, there are consequences to Congress not having come up with a more sensible way to reduce the deficit."

Obama: Gap Between Parties May Be 'Too Wide' for a Grand Bargain on Budget (ABC News)

Obama Publicly Declared for the First Time Chinese Gov't Behind Cyberattacks

"Well, I think [we] always have to be careful [about] war analogies. Because, you know, there's a big difference between them engaging in cyberespionage or cyber attacks and, obviously, a hot war. What is absolutely true is that we have seen a steady ramping up of cybersecurity threats. Some are state sponsored. Some are just sponsored by criminals," he told me.

I asked him to clarify that some were indeed state sponsored.

"Absolutely," he responded.

North Korea's Nuclear Ambitions

I asked the president whether he believed North Korea could now make good on its threats of nuclear action against South Korea and the United States.

"They probably can't, but we don't like margin of error," he began.

But when pressed on whether it was really that close, the president rephrased his response.

"It's not that close. But what is true is … they've had nuclear weapons since well before I came into office. What's also true is missile technology improves and their missile technology has improved," he said.

"Now, what we've done is we've made sure that we've got defensive measures to prevent any attacks on the homeland. And we're not anticipating any of that. But we've seen out of the North Koreans is they go through these periodic spasms of … provocative behavior."

I asked the president whether he believes such recent threats are more serious than previous threats.

"Well, I don't necessarily think it's different in kind. They've all been serious. Because when you're talking about a regime that is oppressive towards its people, is belligerent, has shown itself to sometimes miscalculate and do things that are very dangerous, that's always a problem. "

He 'Couldn't Imagine Circumstances' in Which a State Ban on Same-Sex Marriage Was Constitutional

Before the Supreme Court arguments on same-sex marriage scheduled for the end of the month, I asked the president whether he still believed that the issue was best left to the states, or whether he thinks same-sex marriage was a right guaranteed by the Constitution.

"Well, I've got to tell you that, in terms of practical politics, what I've seen is a healthy debate taking place state by state, and not every state has the exact same attitudes and cultural mores," he said. "What I also believe is that the core principle that people don't get discriminated against, that's one of our core values. And it's in our Constitution."

The president said he personally could not see a scenario in which a state has a legal justification for banning same-sex marriage.

"What I believe is that if the states don't have a good justification for it, then it probably doesn't stand up to constitutional muster," he said.

Obama Rejected Concerns that a U.S. Pope Would Be Too Closely Aligned With U.S. Gov't

Turning across the Atlantic to the papal conclave happening this week, President Obama rejected the notion held by some cardinals that a U.S. pope would be too closely aligned with the U.S. government, an argument frequently used against U.S. cardinals who might be considered contenders for the papacy.

"I guarantee you … the conference of Catholic bishops here in the United States don't seem to be taking orders from me," he said.

"I, my hope is, based on what I know about the Catholic Church and the terrific work that they've done around the world."

The full interview will air tonight on "Nightline," and will also be available on Yahoo! as part of our on-going newsmakers series.